Radio frequency ablation device for the destruction of tissue masses

ABSTRACT

The inventive ablation element comprises an elongated cannula having a proximal end and a distal end. The cannula defines an internal lumen within the cannula and a cannula axis. A plurality of conductors contained within the lumen, each of the conductors has a proximal end proximate the proximal end of the cannula, and a distal end proximate the distal end of the cannula. A plurality of ablation stylets each has a proximal end and a distal end, and each coupled at the respective proximal end of the stylet to the distal end of a respective conductor, the stylets comprise a deflectable material, the conductors together with their respective stylets being mounted for axial movement. A trocar point defined proximate the distal end of the cannula.

This application is a continuation of U.S. patent application Ser. No.11/173,928 filed on Jul. 1, 2005 entitled RADIO FREQUENCY ABLATIONDEVICE FOR THE DESTRUCTION OF TISSUE MASSES, the disclosure of which isincorporated herein by reference.

BACKGROUND

In the United States, approximately 230,000 women have hysterectomiesannually. The primary reason for the performance of these hysterectomiesis the existence of substantial symptoms associated with uterinefibroids. In the United States alone, there are more than six millionwomen with uterine fibroid symptoms that prefer to suffer, rather thanendure the risks and inconveniences associated with surgery, especiallya major surgery that results in infertility. Outside of the UnitedStates, the situation is much the same, with millions of women sufferingwith fibroids in need of a safe alternative to hysterectomy.

Recently, another treatment option (uterine artery embolization) hasbeen introduced. Generally, this procedure involves embolization of thearteries which feed the urine fibroid. This results in cutting off theblood supply to the fibroid and the shrinkage of the fibroid over time.However, the unacceptably high rate of complications severely limits itsappeal to patients.

Myomectomy, which generally involves the surgical removal of the fibroidthrough the use of classical surgical procedures, is another treatmentoption. However, due to its rate of complications and long recoverytime, this option is also not very appealing to patients. Typicalcomplications involve risk of infection, relatively severe postsurgicalpain, damage to the uterus and other risks normally associated with suchtypes of surgery. Moreover, such damage to the uterus may be relativelysubtle and may only come to light when the uterus begins to swell duringpregnancy and ruptures at a weak point created during the surgery,resulting in loss of the fetus.

Still another alternative to treat the discomfort associated withuterine fibroids is the removal of the endometrium which lines theuterus. However, this procedure also results in infertility.

In an attempt to address these issues, an RF ablation probe of the typeused to treat tumors in the human liver by hyperthermia has beensuccessfully demonstrated to substantially shrink or eliminate uterinefibroids.

See, for example, U.S. Pat. No. 6,840,935 issued to Lee on Jan. 11,2005, the disclosure of which is incorporated herein by reference. Inthat patent a method for treating pelvic tumors, such as uterineleiomyomata, includes inserting an ablation apparatus into the pelvicregion and positioning the ablation apparatus either proximate to orinto a pelvic tumor.

The method further includes using a laparoscope and an imaging device,such as an ultrasound machine, to confirm the location of the pelvictumor and placement of the ablation apparatus. An ablation apparatuswith multiple needles or deployable arms that are inserted into thepelvic tumor is disclosed. The method involves deliveringelectromagnetic energy or other energy through the ablation apparatus tothe tumor to induce hyperthermia and tumor ablation.

The particular device disclosed for ablating the tumor in U.S. Pat. No.6,840,935 is of the type disclosed in U.S. Pat. No. 5,728,143, issued toGough et al. on Mar. 17, 1998. Generally, that device comprises aplurality of resilient springy RF ablation antennae or electrodes which,importantly, are preformed with a curved configuration which they assumeafter exiting a sharp trocar-tipped catheter. Generally, as the antennaeexit the trocar tip, they advance long curved paths (extending along arange of different paths in various portions of the tumor to be ablated)which are defined by their preformed springy shapes. The deployedantennae with their particular preformed shapes thus define an ablationvolume. Various shape ablation volumes may be defined by varying theconfiguration of the curves which are preformed into the various springyantennae. Such devices are manufactured by Rita Medical Systems ofMountain View, Calif. Generally, such devices work by the antennaeassuming their pre-formed configuration as they emerge from the trocartip.

SUMMARY OF THE INVENTION

In accordance with the invention, it has been observed that difficultiesare sometimes encountered in using such prior art curved electrodeablation systems. More particularly, it has been observed in accordancewith the invention that fibroid tissues tend to be somewhat moredifficult to pierce compared to other types of tumors and that thisaccounts for the problems encountered. To a limited extent, thedifficulty of piercing the fibroid with the antennae may be mitigated byadvancing very small increments of the ablation antennae into thefibroid, applying radiation t9 the antennae to induce hyperthermia anddegrade the physical integrity of the tissue surrounding the antennae.The antennae may then be advanced into the somewhat deteriorated tissueand the application of radiation to the antennae continued to enlargethe physically deteriorated regions of the tumor, and, after a time,further advancing the antennae.

While this iterative advancement of the antennae, punctuated byrelatively long periods of time during which advancement cannot beimplemented, requiring the physician to wait for the desired degree ofdeterioration of the tissue into which the antennae will next beadvanced, will work to effectively and minimally-invasively ablate thetumor, the procedure is time-consuming compared to a procedure in whichantennae may be fully deployed and radiation applied to a large volumeof the tumor during a single application or limited number ofapplications of RF energy.

Accordingly, while the above procedure has seen some commercialimplementation, the time necessary for the procedure has made itrelatively expensive and thus it is not available to many individuals.Moreover, the skill required for the performance of the procedure isrelatively high, and thus few doctors are able to perform the procedure.Moreover, proliferation of this approach is not likely in view of thesteep learning curve and the small number of individuals competent toperform this procedure. Nevertheless, in accordance with the invention,it is believed that a quick and easy to implement RF ablation procedurewould be very attractive to doctors and patients in view of the low riskof complications and the relatively lower likelihood, under a typicallyencountered set of circumstances, that the uterus will be damaged andfail during a subsequent pregnancy.

In spite of the fact that this method for treating uterine fibroids hasbeen known for a number of years, no such alternative apparatus has beendevised for improving the procedure.

In accordance with the invention, the inventive ablation elementcomprises an elongated cannula having a proximal end and a distal end.The cannula defines an internal lumen within the cannula and a cannulaaxis. A plurality of conductors are contained within the lumen. Each ofthe conductors has a proximal end proximate the proximal end of thecannula, and a distal end proximate the distal end of the cannula. Aplurality of ablation stylets each has a proximal end and a distal end,and each is coupled at the respective proximal end of the stylet to thedistal end of a respective conductor. The stylets comprise a deflectablematerial. The conductors together with their respective stylets aremounted for axial movement. A trocar point is defined proximate thedistal end of the cannula. A deflection surface is positioned betweenthe trocar point and the proximal end of the cannula. The deflectionsurface is configured and positioned to deflect, in response to axialmovement of the sty lets in a direction from the proximate end of thecannula to the distal end of the cannula, at least some of the styletslaterally with respect to the cannula axis in different directions alongsubstantially straight paths. The straight stylet is deflected from itsstraight trocar axis parallel path by the curved trocar guide surface inthe mandrel over a curved or rounded counter surface directly adjacentto the curved track. This arrangement provides for a maximum in theamount of stylet deflection in a given volume. In accordance with theinvention the stylet may only be contacted by guiding surfaces at two orthree points to reduce friction. This rapid and abrupt change indirection is needed to limit the cross sectional area of the deliverycannula that carries the stylets and penetrates into the target tissue.The design of the pathway, the opposing curved surface over which thestylet is bent, the spring characteristics of the stylet and the leveland orientation of the point on the stylet all have to be adjusted tominimize friction and yet maximize the degree of deflection that can beachieved. The stylet may be very easy to bend and take the curve easilybut of insufficient structural integrity to penetrate the target tissue.The stylet may be very rigid but then unable to make the neededdeflection into the tissue. If the bend is made but the friction ofdeployment is too great the instrument might be difficult to use. Evenwithin one tip mandrel a variety of angles may be desired. This isachieved by variously adjusting the curvature of the “paths” in themandrel and the proximity of the rounded counter surface over which thestylet is bent to the depth of the curved path. When these stylets exitthe mandrel into the tissue they define an ablation volume in the targettissue.

Each of the conductors may be selected from the group consisting ofelectrical conductors, radio frequency conductors, microwave conductorsand optical conductors.

Each of the conductors may be integral with its respective ablationstylet. The solid contents of the lumen consist essentially of theconductors. Each of the stylets may be configured to assume asubstantially straight configuration in the absence of external forces.

An ablation element further comprises a a finger operated slider, pliersactivator or motor member or members or other drive system coupled tothe conductors to drive axial movement of the stylets in directions fromthe proximal end of the cannula to the distal end of the cannula, andfrom the distal end of the cannula to the proximal end of the cannulathrough a plurality of positions. The trocar point may be defined at thedistal end of a trocar member. The trocar member has an outside surface.The cannula has an outside surface. The trocar member has a proximal endsecured proximate to the distal end of the elongated cannula. Theoutside surface of the cannula and the outside surface of the trocarpoint define a trocar surface.

The deflection surface comprises a number of ramps defined proximate theproximal end of the trocar point. The distal ends of the stylets arepositionable proximate to the ramps and within the trocar surface.

In the preferred embodiment, the conductors and the stylets areelectrical conductors. Each of the stylets may be configured to assume asubstantially straight configuration in the absence of external forces.

The deflection surface comprises a plurality of channels guiding thedistal ends of the stylets to the ramps. The cannula may be secured tothe trocar member with the outside surface of the cannula proximate tothe outside surface of the trocar member.

An ablation element also comprises an anchor mounted for movementbetween an internal position disposed within the trocar surface and ananchoring position extending laterally from the trocar surface throughpoints external to the lumen. A drive member is disposed within thelumen and coupled to the anchor to drive the anchor between the internalposition and the anchoring position.

The anchor comprises at least two pointed members mounted for movementin directions which have vector components which extend away from theaxis of the cannula and away from each other.

The pointed members extend in a direction with a vector component thatextends in a direction opposite to the direction in which the trocarpoint extends. The conductors bear against each other at least along aportion of their length within the cannula.

The conductors are driven by a drive mechanism which allows theconductors to move independently. The conductors have a length, a widthand a thickness, the width being greater than the thickness, andterminate in a point oriented to allow deflection by the deflectionsurface. The conductors extend in different directions when they exitthe deflection surface and extend to a variable extent.

The anchor members, alone may be utilized as electrodes for ablation oftissue. Alternatively, the anchor members may be used simultaneously incombination with the tip electrodes. When used together, this couldcreate a larger ablation volume within the target tissue as compared tothe ablation volume created when only the tip electrodes have ablativeenergy applied to them. When used alone, the ablation energy applied tothe anchor members alone may be used in anatomic situations whereretrograde deployment of electrodes is desired or even required.

The electrodes may be used in a monopolar fashion with the ablationstylets excited with RF energy and a return electrode being appliedusually in the form a conductive pad in contact with a remote surface onthe patient. Excitation may be applied in a bipolar fashion where oneset of electrodes, such as the tip electrodes could serve as negativeelectrodes and the anchor electrodes may serve as the positiveelectrodes and create an ablation volume between the two sets ofelectrodes.

Separately, a cauterizing RF current can be supplied to the tip mandrelby the RF generator. Surgical RF generators may be separated intogenerators that are designed for ablation, or the controlled heating oftissue to bring about cellular death without charring or desiccation,and electrosurgical RF generators that are well known in the art for theability to char and desiccate tissue for the purpose of coagulation ofvessels to control bleeding, and cutting of tissue for rapid tissuedissection. Electrosurgical generators used for cauterization tend to beof higher power and current than those used for ablation. In accordancewith the invention, cauterizing is delivered to the metal trocar tip ofthe cannula as the cannula is withdrawn to provide for cauterization ofthe track as the cannula is withdrawn. Traditional RF ablationgenerators apply a “track ablate” mode of somewhat higher wattage ofablation energy for this purpose, but do not approximate the energydelivered to the tissue by electrosurgical generators known in the art,as is employed in the present invention.

The conductors are driven by a drive circuit which varies the amount ofenergy supplied to the stylets and/or the length of the stylets and/orthe length of time during which power is supplied to the stylets and/orthe angular orientation of the ablation element.

The parameters of stylet length, stylet power, stylet actuation timeand/or angular orientation may be controlled by a computer in responseto a computer program having an input comprising feedback informationfrom the tissue area being operated on and/or a preset program.

An anchor or anchors are mounted for movement between an internalposition disposed within the trocar surface and an anchoring positionextending laterally from the trocar surface through points external ofthe lumen. A drive member is disposed within the lumen and coupled tothe anchor to drive the anchor between the internal position and theanchoring position. The anchor comprises one two or more pointed membersmounted for movement in a direction which has vector components whichextend away from the axis or the cannula and in the case of two anchors,also extend away from each other.

The front end is a trocar point defined at the distal end of the trocarmember.

The anchors may be deployed in response to rotary motion. The anchorsare deployed by bearing against a deflection surface. The anchors aremade of a springy material which may assume a curved configuration whennot subjected to external forces.

As compared to a conventional hysterectomy, the present invention isthus directed to a device for the treatment of uterine fibroids andother tissue masses that meets the needs of women by conserving theuterus and reducing recovery time from 6 to 8 weeks to 3 to 10 days.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the multiple antenna ablation device ofthe invention;

FIG. 2 is a perspective view of a delivery manual with an anchoringsystem;

FIG. 3 is a front view of the inventive probe with anchor system of thedevice illustrating the trocar before deployment of the anchor;

FIG. 4 is a perspective view of the apparatus of the present inventionwith anchors deployed;

FIG. 5 is a front plan view with nine trocars deployed;

FIG. 6 is a cross-sectional view of an alternative anchoring structure;

FIG. 7 is a cross-sectional view illustrating the position of thedeployed anchors in the embodiment of FIG. 6;

FIG. 8 is a cross-sectional view illustrating another alternativeanchoring structure;

FIG. 9 is a cross-sectional view illustrating the anchoring structure ofFIG. 8 after applying force to actuate the anchors;

FIG. 10 is a cross-sectional view of yet another alternative anchorstructure;

FIG. 11 is a cross-sectional view of the ballooned anchor structure ofFIG. 10;

FIG. 12 is a side plan view illustrating a resilient curvedconfiguration anchoring structure for trocars made of springy wirematerial;

FIG. 13 is a side plan view of a structure with a spiral anchoringdevice;

FIG. 14 is a top plan view illustrating a rotatably deployable anchoringstructure;

FIG. 15 is a perspective view of the anchoring structure of FIG. 14;

FIG. 16 is a cross-sectional view illustrating structure for deploymentof an anchor which extends the entire length of the cannula to asuitable actuation structure;

FIG. 17 is another alternative embodiment of the inventive trocar withstylus emerging substantially vertically to the trocar point;

FIG. 18 is yet another alternative embodiment of the inventive trocarwith stylus emerging in a slightly retrograde fashion relative to thedirection of advancement of trocar point;

FIG. 19 is still yet another alternative embodiment of the inventivetrocar with stylus emerging in a highly retrograde fashion relative tothe direction of advancement of trocar point;

FIG. 20 is a front view of the delivery surface of the embodiment of theinventive trocar comprising a sandwich of a proximal plastic angularmember, a metal mandrel and a distal plastic annular member;

FIG. 21 is a front view of the embodiment of the inventive trocarcomprising a single plastic annular member with a meal guide member;

FIG. 22 is a schematic view of an embodiment of the inventionillustrating the different directions of stylet deployment;

FIG. 23 is a cross-sectional view, along lines 23-23 of FIG. 27, of theplurality of passages with ablation elemental wires;

FIG. 24 is a cross-sectional view illustrating the positions ofdeployment for a first group of stylets;

FIG. 25 is a cross-sectional view illustrating the positions ofdeployment for a second group of stylets;

FIG. 26 is a cross-sectional view illustrating the positions ofdeployment for a third group of stylets;

FIG. 27 is a cross-sectional view along lines 27-27 of FIG. 24;

FIG. 28 is a cross-sectional view along lines 28-28 of FIG. 25;

FIG. 29 is a cross-sectional view along lines 29-29 of FIG. 26;

FIG. 30 is a schematic view illustrating selective ablation withmultiple ablation electrode lengths and variable time exposures;

FIG. 31 is a front view illustrating the structure of yet still anotheralternative trocar constructed in accordance with the present invention;

FIG. 32 is cross-sectional view of the juncture between the trocar pointand the cannula;

FIG. 33 is a cross-sectional view along lines 33-33 of FIG. 32;

FIG. 34 is cross-sectional view along lines 34-34 of FIG. 32;

FIG. 35 is a cross-sectional view of the position and direction ofbending of a stylet in the embodiment of FIG. 32;

FIG. 36 is cross-sectional view along lines 36-36 of FIG. 35;

FIG. 37 is a cross-sectional view illustrating the deployed positions ofthree stylets further downstream from the position illustrated in FIG.36;

FIG. 38 is a cross section view illustrating the deployed configurationsof deflection of three stylets further downstream from the positionillustrated in FIG. 37;

FIG. 39 is a cross-sectional view illustrating the configurations ofdeflection of three stylets further downstream from the positionillustrated in FIG. 38;

FIG. 40 is a cross-sectional view illustrating the direction of thedeployed stylets;

FIG. 41 is a cross-sectional view illustrating the trocar of the presentinvention with relatively flat electrodes;

FIG. 42 is a cross-sectional view illustrating the employment of styletsin the embodiment of FIG. 41;

FIG. 43 is a cross-sectional view illustrating the employment of anchorsin the embodiment of FIG. 41;

FIG. 44 is a cross-sectional view illustrating the position of thedeployed anchor;

FIG. 45 is a cross-sectional view of an ablation trocar with squareshaped stylets;

FIG. 46 is a cross-sectional view of a trocar with irregular shapedstylets; and

FIG. 47 is a schematic cross-sectional representation of low frictionstructure for advancing a stylet from the inventive trocar;

FIG. 48 is a perspective view of an alternative embodiment of theinvention;

FIG. 49 is a cross-sectional view of the embodiment of FIG. 48;

FIG. 50 is a cross sectional view of an operator handle useful with theembodiment of FIG. 48 and of 49; and

FIG. 51 is a perspective view of still another alternative embodiment ofthe invention.

DETAILED DESCRIPTION OF THE BEST MODE

Hyperthermal treatment of tissues of the human body is well established.It has been used for hemostasis, destruction or ablation of tissues,tightening or shrinkage of various tissues and for other purposes. Inaccordance with the invention this and other methods for destruction oftissue may also be deployed, such as the delivery of laser light at highintensity levels, the use of conventional resistive heating elements,and other energy delivery devices which can be deployed within tissue.The source of heating may be varied and includes but is not limited toradiant heating, electrical current, radio frequency or microwaves,ultrasound and others.

A number of methodologies utilize radio frequency heating of tissues forablation or shrinkage by the application of the energy to the tissuesthrough specialized delivery devices. These devices often haveelectrodes or antenna that are placed into, or onto, the tissue to betreated. Some of these systems incorporate monitors that can providefeedback to the operator, or the device system itself, as to theprogress of the treatment. This may be in the form of a readout of thetemperature of various parts of the tissue, how much and over what timethe energy is being delivered, or a feedback control system to theenergy generator itself to control the delivery of energy to the tissue.Often the desired result is the heating of the tissue as quickly anduniformly as possible to destroy the target tissue without charring oftarget tissue or necrosis of tissue which is not being targeted.Charring of target tissue interferes with a uniform and predictableheating of the target tissue.

In accordance with the invention energy delivery devices are providedwhich are adapted to the destruction of target tissue at the site wherethe electrodes are located. Accordingly, the operator can deliver thetreatment safely and effectively. One such target tissue for the devicesof the present invention is a uterine fibroid. A physician may wish toplace an energy delivery device to deliver energy such as radiofrequencycurrent (RF) into the mass of the fibroid in order to cause it to shrinkand become less symptomatic to the patient.

A uterine fibroma is a benign muscle tumor which forms in the wall ofthe female uterus. The tissue is highly vascular, firm and difficult topenetrate even with a sharpened needle. Where ablation of the tumor isto be preformed, it is important for the physician operator to carefullyplace the ablation stylets (for example radiofrequency electrodes) inthe correct positions within the fibroid prior to applying ablativeenergy.

Furthermore, in accordance with the invention, it is recognized that itis useful if the electrodes or their delivery device experience minimalmigration in the forward and backward directions during and after theelectrode placement process.

In accordance with the invention, a device is provided that allowsmultiple straight electrodes (i.e. electrodes substantially withoutcurvature) to be pushed into and through the tough fibroid tumor tissue.The straight electrodes have greater column strength and will havesuperior mechanical advantage over curved electrodes when deployed intothis type of tissue and will permit easier, safer and more accurateplacement. The straight electrodes are directed into the tissue at avariety of angles by a mandrel-like delivery member which serves as adeflection surface. This delivery mandrel does not impart a permanentshape to the electrode. Rather its action is limited to redirecting theelectrode at an appropriate angle. The electrodes can be made of shapememory material such as NiTi.

In addition to the delivery mandrel, an anchor system is provided inaccordance with the invention. A number of alternate designs aredisclosed herein but the same are described by way of example and othersuitable anchor systems may be employed.

The disclosed anchor systems allow the operator to stabilize thedelivery device prior to deployment or withdrawal of electrodes, andthus improve electrode placement. The anchors prevent the device frommigrating backward when pushing the electrodes into the firm tissue orforward when pulling the electrodes out.

The inventive system contemplates a variety of methods where theoperator would apply the anchor, for example prior to electrodeplacement. Alternately, an anchor or anchors may be deployed afterplacement of the ablation electrodes. It is also contemplated inaccordance with the invention that there are circumstances where anchorsmight not be applied at all. Likewise, in accordance with the inventionit is contemplated that anchoring functions may also be performed byablation stylets.

Referring to FIG. 1, an ablation trocar 10 incorporating a plurality ofdelivery mandrel surfaces 12 (FIG. 2) on a trocar point 14 isillustrated. In accordance with the invention, trocar point 14 ismounted on a cannula 16. Cannula 16 may be made of any suitablematerial, such as plastic, or metal (covered with a plastic insulatinglayer, to prevent ablative energy from leaking out of the device alongthe length of the cannula. Trocar point 14 includes a forward piercingedge surface 18. Metal cannulas coated with an insulator are preferredfor their strength.

Cannula 16 defines an internal lumen 20 which carries a plurality ofstylets 22. Stylets 22 are made of a springy conductive material such asa springy nickel titanium alloy. In accordance with the invention, eachof the stylets 22 comprises a long and straight springy wire-like memberwhich may be housed wholly within lumen 20 of cannula 16, as illustratedin phantom lines in FIG. 2. Because the ends of the wire-like stylets 22are exposed, elements that form in the case of electrically conductivestylets for applying RF energy, 28 at their tips which form stylets 22after they exit trocar 10, only the stylets 22 apply ablative energy,and thus tissue surrounding cannula 16 is substantially unaffected,except for the trauma caused by passage of the trocar through thetissue. The stylet may be withdrawn back into a tip mandrel 24 and theRF cauterizing energy applied to the tip mandrel alone during withdrawalof trocar 10 following completion of ablation. When it is decided toadvance the tip 24 of a stylet into a tissue mass to be subjected toablation, tip 24 is advanced in the direction of arrow 26. Improvedpiercing may be obtained by sharpening the tip 24 to form a point 24 a,as illustrated in phantom lines in FIG. 1. As tip 24 is advanced, itbears against surface 12, which deflects it as is more fully describedbelow. The result is to cause the stylets 22 to be laterally deflectedand assume the configuration illustrated in FIG. 1.

Stylet 22 may be left in the position illustrated in FIG. 1 duringwithdrawal of the trocar, and may be driven with RF energy or othersuitable input during withdrawal to achieve canterization of theelongated wound which formed the path of the trocar.

Referring to FIG. 2, ablation trocar 10, mounted on cannula 16 includesa collar 28 secured to a plurality of axially oriented ridges 30disposed around the circumference adjacent cannula 16. Collar 28 isrigidly secured to ridges 30 and is in spaced relationship tosubstantially concentric inner sleeve 32 Inner sleeve 32 is slidablymounted within cannula 16 and is secured to and supports trocar point 14Inner sleeve 32 may be made of plastic or other flexible material.

A plurality of anchors 34 are secured by numerous means such asfasteners 36 or laser welding to inner sleeve 32. Anchors 34 terminateat points 38 which are sharpened to easily pierce the tissue and thusanchor the trocar. Anchors 34 are disposed in the space between collar28 and inner sleeve 32, and are adapted to slide in the directionsindicated by arrows 26 and 40. Anchors 34 are made of a springy materialand except for the influence of collar 28 would assume the positionillustrated in phantom lines in FIG. 2.

Cannula 16 also supports and is rigidly connected to a plurality ofdeflection surfaces 42 against which points 38 bear during the anchoringprocedure, as will be described in detail below. Deflection surfaces 42may be formed on a single annular member which is fitted on to andaround the end of cannula 16 and which includes a plurality of arcuatesurfaces 44 which bear against and may be glued or otherwise secured tothe outer surface 46 of cannula 16.

In accordance with the invention, a wide variety of materials may usedto manufacture the inventive trocar 10. For example, all members may bemade of plastic except for the very tip of forward piercing edge surface18 and stylets 22.

When it is desired to use the inventive ablation trocar 10, for exampleto ablate a uterine fibroid, trocar 10 is put into the configurationillustrated in FIG. 3. In this position, the points 24 of each of thestylets 22 are not deflected and positioned at the input of the deliverymandrel surfaces 12. Ablation trocar 10 is then advanced, in the case ofa uterine fibroid, into the uterus in the manner described in theabove-incorporated patent of Lee. Alternatively, the inventive trocarmay be inserted through other paths, depending upon the location of theparticular fibroid to be destroyed or other factors.

Once the trocar point 14 and those parts of ablation trocar 10 proximatethereto are in position for the deployment of ablation stylets 22,anchoring may be implemented by withdrawal of inner sleeve 32 intocannula 16. As sleeve 32 is withdrawn into cannula 16, it pulls anchors34 in the direction indicated by arrow 40, pushing anchor points 38against deflection surfaces 42, causing the flexible resilient anchors34 to be deflected laterally in the directions illustrated in FIG. 4,under the combined influence of the inner surface of collar 28 anddeflection surfaces 42 which induce an outward lateral bend.

In accordance with the present invention it may be desired that theanchors be relatively rigid and strong. Accordingly, in order to achievethe desired amount of bending in such a rigid member, the anchors are ofa flat cross-section.

Also in accordance with the invention, the anchors may be made of aconductive material and driven with RF energy to serve as ablationstylets.

As the anchors are advanced with their tips moving in the directionindicated by arrow 48, they pierce the surrounding tissue and thusanchor the trocar point 14 against retrograde motion when stylets 22 areadvanced. The stylets are advanced by causing them to move from theposition illustrated in FIG. 3 in the directions of arrow 26. Thiscauses them to bear against delivery mandrel surfaces 12, deflectingthem laterally and outwardly in the directions indicated by arrows 50(FIG. 1). This results in the distal end of the trocar 10 taking theconfiguration illustrated in FIG. 1.

While the arrangement of stylets may be may to form any desired pattern,in the illustrated embodiment, a cone is achieved as can be seen withreference to FIGS. 1 and 5.

If desired, anchors may first be deployed one at a time to minimizeunwanted displacement of the distal end of trocar 10. Likewise, ifdesired, anchors may not be deployed. An implementation of a use of theinventive trocar 10 without the anchors would be promoted by advancingthe ends of stylets 22 one at a time, thus minimizing their tendency todisplace the trocar.

Moreover, in accordance with the invention, the advancement of styletssingly, in combination or in any desired pattern, as well as thecontrolled single, multiple or other advance in a pattern for anchorsmay be controlled by an electronic control circuit, microprocessorcomputer or any other system, thus simplifying controls on the deviceheld by the physician. Likewise, any desired steering system may beincorporated into the trocar, in addition to or as a substitute formanual manipulation of the uterus during the advancement of the trocarto and through the target tissue.

In accordance with the present invention, the wires which comprisestylets 22 extend from the distal end of trocar 10 to the proximal endof trocar 10, not illustrated, where they may be connected to suitableadvancement and retraction mechanisms. Such mechanisms may be of aconventional design. However, in accordance with the invention, the samemay be motorized and/or computerized to operate automatically insynchronous or sequential fashion. Also, in accordance with theinvention, the patterns of anchor and/or electrode deployment may bevaried to achieve any desired effect.

After the stylets 22 have been successfully deployed in the tumor massto be ablated, RF energy, in the instant example, is applied to thestylets using a signal intensity sufficient to heat target tissue to asufficiently high temperature to result in hyperthermia and consequentdestruction of the target tissue. However, care must be taken not toapply too much energy to the target tissue because charring of thetarget tissue in a very narrow region surrounding the stylet will createan insulative jacket around the stylet, preventing enough RF energy frompassing through and reaching the target tissue beyond the jacket insufficient quantities to result in ablation of that portion of thetarget tissue.

Referring to FIG. 6, an alternative anchoring structure for an ablationtrocar 110 including ablation electrode structure of the typeillustrated in FIGS. 1-5 is shown. The trocar 110 illustrated in FIG. 6includes a pair of anchors 134 mounted on arms 135 which are mounted forrotation about living hinges 137. Arms 135 rotate in the directionsindicated by arrows 139.

Trocar 110 may be used in the same manner as the trocar illustrated inFIGS. 1-5. After being advanced through the piercing action of forwardpiercing edge surface 118, anchors may be deployed. When it is desiredto deploy the anchors, actuator 141 is advanced in the direction ofarrow 143, resulting in the point of trocar 110 taking the positionillustrated in FIG. 7.

When the doctor desires to remove the trocar or advance it to anotherposition, actuator 141 is withdrawn to the position illustrated in FIG.6, causing arms 135 to assume the position illustrated in FIG. 6 onaccount of the arms 135 resiliently returning to their originalposition. In accordance with the invention, the anchor may be formed bya plurality, for example, of resilient arms 135 mounted on a tubularmember 145. Tubular member 145, resilient arms 135, and anchoring points134 may be made integral with each other and made of a plastic capableof taking a point.

Still yet another anchoring structure is illustrated in FIG. 8. Inablation trocar 210, cannula 260 includes a plurality of slits 217. Bythe application of force bringing trocar point 214 closer to cannula216, the fingers 219 defined between slits 217 may be crimped asillustrated in FIG. 9. The result is the definition of points 221, whichwill tend to lock into surrounding tissues to anchor trocar 210.

Yet another anchoring structure for a trocar 310 is illustrated in FIG.10. Here an intermediate section 317 capable of ballooning asillustrated in FIG. 11 is utilized as an anchoring structure.

Referring to FIG. 12, a trocar 410 with the yet another anchoringmechanism is illustrated. In this embodiment, anchors 435 are formed ofa resilient metal and have points 435. Anchors 434 are preformed with aresilient curved configuration. In other words, anchors 434 are made ofa springy wire material which is a delivered in a relatively straightconfiguration conforming to the path along which the trocar is advancedbecause they are located in cannula 416. Upon exit from trocar 410,anchors 434 tend to take the illustrated curved configuration, whichthey springingly return to when not subjected to external forces. Theanchors thus extend along and in cannula 416, exiting near the distalpoint 414 of the trocar. The anchors are advanced from the cannula inthe same manner as the ablation electrodes in the embodiment of FIGS.1-5. In accordance with this embodiment of the invention, stylets 422(shown in the retracted position in the figure may be advanced out oftrocar point 414 in the manner of the embodiment of FIGS. 1-5.

Yet another approach is illustrated in FIG. 13, where trocar 510includes a spiral anchor 435, which may, for example, surround the endof the cannula. Spiral anchor 435 may be rotated to advance anchor point434 into the tissue adjacent the area to be ablated.

In accordance with the invention, it is also possible to utilized ananchoring structure such as that illustrated in FIGS. 14 and 15. Inaccordance with this system, the cannula of the trocar incorporatesfeed-through cowls 517 defined in an anchor housing 519. Anchors 534 areadvanced out through cowls 517 by being driven with circumferentialmotion in the directions indicated by arrow 543. Alternatively, they maybe retracted by advancement in the opposite direction indicated by arrow539.

Referring to FIG. 16, still yet another possibility is the employment ina trocar 610, including a cannula 616, which contains anchors 634 at theend of wire like elements which extend the entire length of the cannulato a suitable actuation structure. Such anchors 634 may be driven in thedirection indicated by arrow 643. Anchors 634 are driven out by deliverymandrel surfaces.

It is noted that the various anchoring mechanisms illustrated in FIGS.6-16 may be used with any of the ablation electrode structuresillustrated in the various embodiments of the invention described hereinor with similar ablation electrode arrangements.

Turning to FIG. 17, an alternative embodiment of the trocar 710constructed in accordance with the present invention is illustrated. Inaccordance with this embodiment, ablation stylet 722, which is anelectrode, passes within the walls of the cannula 716 which has aplurality of passages 717, which may be positioned at equal intervalsalong the circumference of cannula 716 and wholly within the sidewall ofcannula 716. Thus, during use, stylets 722, after exiting deflectionpassages 711 in delivery member 712, pierce the surrounding tissuethrough the action of points 724. Good physical integrity is achieved byhaving a metal trocar point 714 secured to the distal end of centralaxial member 715, which is also metal, which may also be thinned toallow additional volume for the deflection of the ablation electrode.Delivery member 712 may be made of metal to accommodate relatively highdegrees of angular deflection by passages 711. Such greater degrees ofangular deflection and a thinned central axial member are illustrated inFIG. 18, which has a stylet 722 a with a slightly rearward motion beingangled toward the proximal and of the trocar. FIG. 19 illustrates aneven more retrograde path for stylet 722 b.

As illustrated in FIG. 20, the delivery surface of this embodiment ofthe inventive trocar 810 may comprise a sandwich of a proximal plasticangular member 809, a metal mandrel 812 and a distal plastic annularmember 813. Distal plastic annular member 813, in turn, provides supportfor trocar point 814.

Alternatively, as illustrated in FIG. 21, another embodiment of theinventive trocar 810 a may comprise a single plastic annular member 809a with a metal guide member 812 a. It is noted that the angle of point824 is oriented to provide for easy sliding motion of stylet 822 indelivery passage 811.

In accordance with one embodiment of the invention, as illustratedschematically in FIG. 22, a trocar 910 may include rearwardly andproximally extending stylets, comprising, for example, radiofrequency orRF ablation electrodes 921. Substantially vertically exiting electrodes922 are also included in this embodiment of trocar 910. Finally, thesame trocar 910 also includes distally extending RF electrodes 923.Radiofrequency ablation electrodes 921, 922 and 923 are advanced in thedirections of arrows 949, 950 and 951, respectively, during deploymentof the electrode into target tissue.

In connection with the embodiment illustrated schematically in FIG. 22,it is noted that stylets 921 may be deployed before stylets 922 and 923,because they are facing in the direction opposite that of the trocarpoint 914 and will thus effectively act to anchor trocar 910.

The provision of multiple electrodes extending in different directions,as schematically illustrated in FIG. 22 may be used to define the shapesof various ablation volumes.

Further variations in ablation volume may be achieved by varying (forexample, in accordance with the present invention by computer) theextent to which stylets 921-923 are extended from the distal end oftrocar 910.

This may be most easily understood with reference to FIGS. 23-30. Inthis embodiment of the invention, trocar 910, like the trocarsillustrated in FIGS. 20-21, include an insulative plastic cannula 916which defines a plurality of passages for the wires which form stylets922. As shown in FIG. 23, at the proximal end of the trocar, the wirescorresponding to nine stylets 922 are arrayed in circumferential form,surrounding central axial member 909, and within passages defined bycannula 916.

Proceeding further downstream from the proximal end of trocar 910 towardthe distal end of trocar 910, deflection surfaces 912 appear. As stylets922 are advanced, their pointed ends 924 advance against surfaces 912and stylets 922 are deflected by surfaces 912, as illustrated by stylet922′ in FIG. 24.

Proceeding further downstream, only six ablation electrodes 922 remain,as illustrated in FIG. 25, on account of the exit of three electrodes atthe position illustrated by the cross-section of FIG. 24. Finally,proceeding further downstream, only three ablation electrodes arepositioned in cannula 916, as illustrated in FIG. 26.

In accordance with the present invention greater degrees of bending maybe achieved by variation of the path of the trocar ablation electrodesfrom the simple paths illustrated in solid lines in FIGS. 24-26. Moreparticularly, at the position illustrated in FIG. 25, the ramp 912 a maybe configured to deflect ablation electrode 922 along a longer pathwithin the deflection member which defines the deflection surfaces. Theresult is a deflected shape for electrode 922 a illustrated in phantomlines in FIG. 25. The same may be more easily understood with referenceto FIG. 28. Likewise, with reference to FIG. 26, an even greater degreeof the rearward bend can be achieved, as illustrated in phantom lines inFIG. 26, and in FIG. 29 by deflection by ramp surface 912 b.

As noted above, variations in ablation volume may be achieved by varyingthe extent to which stylets are extended from the distal end of thetrocar and the direction in which stylets extend. Still yet additionalvariation may be obtained by control the extension of stylets as afunction of time to achieve the desired amount of tissue ablation. Suchcontrol may be achieved using electromechanical systems under thecontrol of a microprocessor or other computing device, such as apersonal computer.

Still yet another method of controlling the ablation volume after theintroduction of the distal end of the trocar into the proximity of thetissue to be ablated is the extension of stylets as described above,followed by the retraction of the stylets, followed by rotation of thetrocar about its axis, followed by again extending stylets as describedabove, followed by again retracting the stylets, and so forth until thedesired ablation volume has been ablated. It is noted that in accordancewith the invention, this may be done in conjunction with power control,time control, extension control and the other techniques describedherein. Such rotation may be done manually by the physician, or may beautomatically done by the device. Such automatic rotation and othercontrol of stylet deployment may be done in accordance with apredetermined sequence, and/or in response to measured conditions in thetissue to be ablated, such as the measurement of temperature, resistanceand so forth, and/or artificial intelligence analysis of imageinformation. Moreover, such control may be done by direct mechanicalcontrols, for example using position transducers to determine the amovement of stylets and angular inertial detectors to determine trocarrotation. Alternatively, imaging and feedback control may be employed.

The wide range of flexibility of the inventive system may be understoodwith reference to FIG. 30. By way of example, trocar 1010 may initiallybe used to perform ablation with stylets 1022 deployed in the positionas illustrated in solid lines. Electrodes 1022 would then be activated,resulting in ablation of volumes 1052 and 1054. After a period of timestylets 1022 may be withdrawn to the positions illustrated in dashedlines. Continued application of RF energy by the stylets will thenablate the remaining portion of volume 1056. Following this procedure, arelatively uniform heating of the tissue to be ablated can be achieved.

In accordance with the present invention it is recognized that thetissue of the uterus is relatively fragile and that its walls arerelatively thin. Accordingly, tissue damage may impair uterusfunctionality during pregnancy and increase the likelihood of a loss ofa pregnancy. Accordingly, a trocar structure which minimizes the size ofthe hole made by the trocar when it is being deployed into the bodywould result in significant advantages. Such an embodiment isillustrated in FIGS. 31-40.

Generally, trocar 1110 comprises a delivery surface 1112 (FIG. 40) builtintegrally with a trocar point 1114. Trocar 1110 comprises a plasticinsulative sleeve forming a cannula 1116. Pins 1158 secure cannula 1116to point 1114. Point 1114 include surfaces 1112 for guiding stylets 1122into the tissue surrounding deployed ablation trocar 1110. As shown inFIG. 33, the wires which form stylets 1122 extend substantially thelength of the trocar and is of minimal size for the number ofstylets/anchors to be deployed. It is also noted that the wires whichform stylets 1122 may be viewed as anchors, depending upon the angle atwhich they exit the delivery surface 1112 of point 1114.

Proceeding further downstream from the proximal to the distal end, thewires which form stylets 1122 fit into a metal or plastic superstructureassociated with point 1114. Proceeding further downstream the outersurface of the catheter, previously formed by cannula 1116, is insteadformatted by point 1114. In the view illustrated in FIG. 36, several ofthe stylets 1122 are illustrated in a deployed position. In connectionwith this, it is noted that, by way of example, only three of thestylets need be deployed at this point in the trocar.

However, proceeding further downstream toward the distal end of thetrocar 1110, as illustrated in FIG. 37, another three stylets may bedeployed. Next, as illustrated in FIG. 38, proceeding further downstreamanother three stylets 1122 may be deployed, leaving behind threeremaining stylets/anchors. In connection with this, it is noted that theonly difference in this embodiment between a stylet and an anchor is thefact that radiofrequency energy is applied to a stylet, whereas ananchor may be left in place without the application of energy. Inconnection with this, it is noted that an anchor to which radiofrequencyenergy is applied will, in addition to performing its anchoring functionact as a tissue ablation electrode.

Finally, as illustrated in FIG. 39, three stylets 1122 may be deployedas illustrated in FIG. 39 and FIG. 40. In connection with thisembodiment, it is noted that these last three stylets may serve thefunction of also being anchors because they are advanced in thedirection of arrow 1150 and thus will tend to drive trocar point 1114forward in the direction of arrow 1126.

An even more efficient use of the width of the trocar is illustrated inFIGS. 41-44. In this embodiment trocar 1210 utilizes a cannula 1216which is completely filled with stylets 1222. FIG. 41 illustrates thetrocar 1210 at a point relatively close to the proximal end of thetrocar. Two of the stylets, namely stylets 1223, act as anchors. Theremaining stylets may be deployed as illustrated in FIG. 42. Thereafterproceeding further downstream, toward the distal end of the trocar, thetwo anchors 1223 may be deployed as illustrated in FIGS. 43 and 44.

Moreover, in accordance to present invention, other sizes and shapes ofstylets may be used. For example, as illustrated in FIG. 45, a trocar1310 may include square cross-section stylets 1322 and flat stylets1323. Similarly, irregular shapes may be employed as illustrated in FIG.46. Moreover, stylets may include stylets made of different materialssuch as materials of different conductivity. For example, anchors 1423and stylets 1422 may be made of one material while stylets 1421 may bemade of another material, perhaps having a different conductivity,flexibility, and so forth.

Turning to FIG. 47, a trocar 1510 includes a point 1514 which defines afirst bending surface 1511 and a second bending surface 1512 whichdeflect stylets 1522, but which define voids 1523 and 1525, adjacentsurfaces 1527 of the stylets 1522 which have no mechanical membersbearing against them. This has the result of achieving low frictiondeflection. Generally, it is contemplated, in accordance with onepossible way of implementing the invention, that friction is to beminimized by making the stylet only as thick as is necessary, for amaterial of the particular resiliency of the material used, to allow thestylet to be advanced through the target tissue. This results in theapplication of minimal force to the stylet by the deflecting members,thus reducing friction.

At the same time, the surfaces doing the deflecting are not a singlecontinuous surface. Rather, two (and optionally more) deflectionsurfaces are positioned to deflect the stylet while at the same timerelying on the natural tendency of the springy metal of which the styletis made, to assume a particular radius. This takes advantage of in theinventive concept of deflecting the stylet without the need for having asubstantially continuous surface in contact with the stylet.

Point 1614 may be driven during trocar withdrawal by a relatively highRF signal to cauterize the entry wound.

Referring to FIG. 48-50, an alternative design for a trocar 1610 inaccordance with the invention is illustrated. Deflection surfaces 1612are defined in a trocar point 1614 and provide for the deflection ofstylets 1622. Trocar point 1614 is secured to a hypotube 1615. Theoutside surface 1617 of hypotube 1615 is coated with an insulativematerial. Hypotube 1615 is made of metal in accordance with thepreferred embodiment on account of the strength of metal having therelatively small dimensions required by the inventive trocar. Whileother materials may be used, presently it is preferred, in the subjectembodiment and the other embodiments illustrated in the application,that the inventive trocar incorporate cannulas made of metal.

Hypotube 1615 houses a plurality of metal members whose ends formstylets 1622.

Hypotube 1615 is slidably mounted within a second cannula or hypotube1619 whose outside surface 1621 is also coated with an insulativematerial. Hypotube 1619 is also preferably made of metal on account ofthe stiffness and strength of the metal.

Hypotube 1619 is rigidly secured to deflection member 1638. Deflectionmember 1638 includes a deflection surface 1639 and a counter surface1640 between which anchor members 1641 are deflected. More particularly,when deflection member 1638 moves in the direction of arrow 40 withrespect to hypotube 1615, it causes anchors 1641 to be deflected from astraight orientation parallel to the axis of trocar 1610 (similar to theposition of anchors 34 in FIG. 3) to the position illustrated in FIGS.48 and 49.

Relative motion of the two hypotubes is achieved by use of a handle 1651incorporating a first slider member 1653 coupled to hypotube 1615, and asecond slidably mounted member 1655 coupled to hypotube 1619. Hypotubes1615 and 1619 are slidably mounted within handle 1651 and are rigidlycoupled to slider members 1653 and 1655, respectively, thus providingfor movement of these members at the ablation end of trocar 1610illustrated in FIGS. 48 and 49. Power to the stylets 1622 is provided byany suitable source coupled to connector 1655.

If desired, an insulative member in 1657 may be provided to ensureelectrical isolation between trocar point 1614 and deflection member1638.

Yet another alternative embodiment of the invention is illustrated andFIG. 51. In this embodiment, a trocar 1710 including a plurality ofdeflection surfaces 1712 defined in a trocar point 1714 andcountersurfaces 1711 on member 1738. Deflection of anchors in 1741 isperformed by a slidably mounted Teflon member 1737, mounted on ahypotube which may be drawn away from the handle at the distal end oftrocar 1710 to deploy anchors 1741 as illustrated in FIG. 51.

While illustrative embodiments of the invention have been described, itis, of course, understood that various modifications will be obvious tothose of ordinary skill in the art in view of the teachings of thisspecification. Such modifications are within the spirit and scope of theinvention as limited and defined only by the appended claims.

While the inventive device has been illustrated for use in the ablationof uterine fibroids, it is understood that this particularimplementation is exemplary and that the inventive device may beemployed in a wide variety of circumstances.

1. An ablation instrument, comprising: (a) an elongated cannula having aproximal portion and a distal portion, said cannula defining an internallumen within said cannula and said cannula defining a cannula axis; (b)at least one conductor extending along at least a portion of the lengthof said lumen, said conductor having a proximal portion proximate theproximal portion of said cannula, and a distal portion proximate thedistal portion of said cannula; (c) a plurality of ablation stylets eachhaving a proximal portion and a distal portion, each of said styletscoupled at the respective proximal portion of each of said stylets tothe distal portion of said conductor, said stylets comprising aresiliently deflectable material said conductor together with saidstylets being mounted for axial movement along at least a portion ofsaid conductor and stylets, said ablation stylets having a substantiallystraight configuration in the absence of the application of externalforces; (d) a head positioned proximate to the distal portion of saidcannula, said head being secured proximate the distal portion of saidcannula, said head having a proximal portion and a distal portion, andsaid distal portion of said head comprising a head end; and (e)deflection surfaces positioned between said head end and said proximalportion of said cannula, said deflection surface being positioned closerto said head end, the deflection surfaces each being configured andpositioned, in response to axial movement of said stylets, to deflect atleast some of said stylets laterally and only outwardly along pathswhich extend away from said cannula axis causing said stylets to exitsaid deflection surfaces and move along substantially straight externalpaths external to said cannula and head, deflection by said deflectionsurfaces achieving most of the deflection in the path of the stylets. 2.An ablation instrument as in claim 1, wherein said conductor is selectedfrom the group consisting of electrical conductors, radio frequencyconductors, microwave conductors and optical conductors.
 3. An ablationinstrument as in claim 1, wherein each of said conductors is integralwith its respective ablation stylet.
 4. An ablation instrument as inclaim 1, further comprising: (f) a motor member or members coupled tosaid conductors to drive axial movement of said stylets in directionsfrom said proximal end of said cannula to said distal end of saidcannula, and from said distal end of said cannula to said proximal endof said cannula through a plurality of positions.
 5. An ablationinstrument as in claim 1, wherein said head end is defined at the distalend of a trocar member, said trocar member having an outside surface,and said cannula having an outside surface, said trocar member having aproximal end secured proximate to the distal end of said elongatedcannula and a distal end which a defines a trocar point.
 6. An ablationinstrument as in claim 5, wherein said deflection surface comprises anumber of ramps defined proximate the proximal end of said trocar point,the distal ends of said stylets being positionable proximate to saidgrooves and at least partially within said trocar.
 7. An ablationinstrument as in claim 6, wherein said conductor is an electricalconductor, said stylets are electrical conductors, and each of saidstylets are configured to assume a substantially straight configurationin the absence of external forces.
 8. An ablation instrument as in claim1, wherein said stylets have a curved surface and said deflectionsurface comprises a plurality of faceted channels guiding said distalends of said stylets.
 9. An ablation instrument as in claim 7, whereinsaid cannula is secured to said trocar member with the outside surfaceof said cannula proximate to the outside surface of said trocar member.10. An ablation instrument as in claim 1, further comprising: (f) ananchor mounted in said instrument, said anchor extending rearwardly whenwithin said instrument for movement between an internal positiondisposed within said instrument and an anchoring position wherein saidanchor extends radially outwardly from said instrument and external ofsaid lumen; and (g) a drive member disposed within said lumen andcoupled to said anchor to drive said anchor between said internalposition and said anchoring position.
 11. An ablation instrument as inclaim 10, wherein said anchor comprises at least two pointed membersmounted for movement in directions which have vector components whichextend away from the axis of said cannula and away from each other andrearwardly and away from head.
 12. An ablation element, comprising: (a)an elongated cannula having a proximal end and a distal end, saidcannula defining an internal lumen within said cannula and a cannulaaxis; (b) a conductor contained within said lumen, said conductor havinga proximal end proximate the proximal end of said cannula, and a distalend proximate the distal end of said cannula; (c) a plurality ofablation stylets each having a proximal end and a distal end, and eachcoupled to the conductor, said stylets comprising a deflectable materialsaid conductor together with said stylets being mounted for axialmovement; (d) a stylet mechanical drive member coupled to said ablationstylets; (e) a front end proximate the distal end of said cannula; (f)an anchor mounted for movement between an internal position disposedsubstantially within said trocar surface and an anchoring positionextending laterally and/or rearwardly away from said front end and fromsaid trocar surface through points external of said lumen; and (g) ananchor drive member separate from said stylet mechanical drive member,said anchor drive member disposed within said lumen and coupled to saidanchor to drive said anchor between said internal position and saidanchoring position, wherein said anchor comprises at least two pointedmembers mounted for movement in directions which have vector componentswhich extend away from the axis of said cannula and away from eachother.
 13. An ablation element as in claim 11, wherein said front endcomprises a trocar point defined at the distal end of a trocar member,said trocar member having an outside surface, said cannula having anoutside surface, said trocar member having a proximal end securedproximate to the distal end of said elongated cannula, and the outsidesurface of said cannula and the outside surface of said trocar pointdefine a trocar surface.
 14. An ablation element as in claim 13, whereinsaid trocar member bears a deflection surface, said deflection surfacecomprising a number of ramps defined proximate the proximal end of saidtrocar point, the distal ends of said stylets being positionableproximate to said ramps and within said trocar surface.
 15. An ablationelement as in claim 12, wherein said anchors when positioned in saidcannula extend in directions which have vector components which extendaway from the distal end of said of ablation element.
 16. An ablationelement as in claim 12, wherein said anchors are deployed in response torotary motion.
 17. An ablation element as in claim 12, wherein saidanchors are deployed by bearing against a deflection surface.
 18. Anablation element as in claim 12, wherein said anchors are made of aspringy material which assumes a curved configuration when not subjectedto external forces.
 19. An ablation element, comprising: (a) anelongated cannula having a proximal end and a distal end, said cannuladefining an internal lumen within said cannula and a cannula axis; (b) aconductor contained within said lumen, said conductor having a proximalend, and a distal end proximate the distal end of said cannula; (c) aplurality of ablation stylets each having a proximal end and a distalend, and each coupled to said conductor, said stylets comprising aresiliently deflectable material said conductors together with theirrespective stylets being mounted for axial movement; (d) a head memberdefined proximate the distal end of said cannula; and (e) a deflectionsurface comprising a bending surface and a counter surface, positionedbetween said head member and said proximal end of said cannula, thebending surface being configured and positioned to deflect, in responseto axial movement of said stylets in a direction from said proximal endof said cannula to said distal end of said cannula, at least some ofsaid stylets laterally with respect to said cannula axis in differentdirections along substantially straight paths, said paths defining anablation volume, the region of contact between a particular one of saidstylets and said bending surface being separated from the region ofcontact between said particular one of said stylets and said countersurface.